From: Kees Cook <keescook@chromium.org>
To: Sean Christopherson <seanjc@google.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
Robert Dinse <nanook@eskimo.com>
Subject: Re: [PATCH 4/4] KVM: x86: Use 16-bit fields to track dirty/valid emulator GPRs
Date: Thu, 26 May 2022 08:41:04 -0700 [thread overview]
Message-ID: <202205260840.3B83593@keescook> (raw)
In-Reply-To: <20220525222604.2810054-5-seanjc@google.com>
On Wed, May 25, 2022 at 10:26:04PM +0000, Sean Christopherson wrote:
> Use a u16 instead of a u32 to track the dirty/valid status of GPRs in the
> emulator. Unlike struct kvm_vcpu_arch, x86_emulate_ctxt tracks only the
> "true" GPRs, i.e. doesn't include RIP in its array, and so only needs to
> track 16 registers.
>
> Note, having 16 GPRs is a fundamental property of x86-64 and will not
> change barring a massive architecture update. Legacy x86 ModRM and SIB
> encodings use 3 bits for GPRs, i.e. support 8 registers. x86-64 uses a
> single bit in the REX prefix for each possible reference type to double
> the number of supported GPRs to 16 registers (4 bits).
>
> Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
--
Kees Cook
next prev parent reply other threads:[~2022-05-26 15:41 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-25 22:26 [PATCH 0/4] KVM: x86: Emulator _regs fixes and cleanups Sean Christopherson
2022-05-25 22:26 ` [PATCH 1/4] KVM: x86: Grab regs_dirty in local 'unsigned long' Sean Christopherson
2022-05-26 14:04 ` Vitaly Kuznetsov
2022-05-26 15:33 ` Kees Cook
2022-05-25 22:26 ` [PATCH 2/4] KVM: x86: Harden _regs accesses to guard against buggy input Sean Christopherson
2022-05-26 14:07 ` Vitaly Kuznetsov
2022-05-26 15:49 ` Sean Christopherson
2022-05-26 15:58 ` Vitaly Kuznetsov
2022-05-26 15:39 ` Kees Cook
2022-05-26 16:01 ` Sean Christopherson
2022-05-25 22:26 ` [PATCH 3/4] KVM: x86: Omit VCPU_REGS_RIP from emulator's _regs array Sean Christopherson
2022-05-26 2:55 ` kernel test robot
2022-05-26 15:47 ` Sean Christopherson
2022-05-26 15:47 ` Sean Christopherson
2022-05-25 22:26 ` [PATCH 4/4] KVM: x86: Use 16-bit fields to track dirty/valid emulator GPRs Sean Christopherson
2022-05-26 15:41 ` Kees Cook [this message]
2022-05-26 1:48 ` [PATCH 0/4] KVM: x86: Emulator _regs fixes and cleanups Robert Dinse
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